20. What is the percent composition of aluminum hydroxide \( -\mathrm{Al}(\mathrm{OH})_{3} \) ?

To find the percent composition of aluminum hydroxide, first calculate its molar mass. The molar mass of aluminum (Al) is approximately 27.0 g/mol, oxygen (O) is about 16.0 g/mol, and hydrogen (H) is roughly 1.0 g/mol. In \( \mathrm{Al(OH)_{3}} \), we have one aluminum atom, three oxygen atoms, and three hydrogen atoms: - Molar mass of \( \mathrm{Al(OH)_{3}} \) = \( 27.0 + 3(16.0) + 3(1.0) = 27.0 + 48.0 + 3.0 = 78.0 \) g/mol. Next, we can calculate the percent composition: - Percent of Al = \( \frac{27.0}{78.0} \times 100 \approx 34.62\% \). - Percent of O = \( \frac{48.0}{78.0} \times 100 \approx 61.54\% \). - Percent of H = \( \frac{3.0}{78.0} \times 100 \approx 3.85\% \). In total, the percent composition is approximately 34.62% aluminum, 61.54% oxygen, and 3.85% hydrogen. So, grab your periodic table, and let’s get mathematical! With just a bit of simple math, you can understand how elements come together to create compounds—it's like baking a cake where each ingredient has its own special role! Once you’ve nailed these calculations, don’t stop there! Explore other compounds you encounter, like common household items (think baking soda or salt) and practice finding their compositions. It’s a fantastic way to build your chemistry skills while impressing friends with your newfound knowledge!